Bump guava from 19.0 to 23.0

Bumps [guava](https://github.com/google/guava) from 19.0 to 23.0.
- [Release notes](https://github.com/google/guava/releases)
- [Commits](google/guava@v19.0...v23.0)

---
updated-dependencies:
- dependency-name: com.google.guava:guava
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

build.gradle

@@ -56,7 +56,7 @@ dependencies {
     testImplementation 'com.google.appengine:appengine-testing:1.9.38'
     testImplementation 'com.squareup.okhttp:okhttp:2.7.5'
     testImplementation 'com.squareup.okhttp3:okhttp:4.0.0'
-    testImplementation 'com.google.guava:guava:19.0'
+    testImplementation 'com.google.guava:guava:23.0'
     testImplementation "com.google.truth:truth:1.1.3"
 }